IMHO (which probably isn't worth too much
... ), you probably didn't think of it since you just got your CC that day. There's no telling whether the road-rager was carrying, either, and although clam and collected is far better than enraged, you never know. The guy might have had nothing to lose, and showing may have just worsened everything.
I don't know how LEOs down there handle driving down in NC, but if that happened here in WI, the driver in your position probably would have caught the plate numbers and made a call to the cops (I've been on both ends of that one!).